The invention relates to method for operating a web-fed printing press.
Web-fed printing presses, such as newspaper printing presses, for example, are extremely complex and highly productive mechanical systems. When operating a web-fed printing press, starting up the web-fed printing press is one of the most complex processes during production. Thus, start-up of a web-fed printing press must take place using a time table that is meticulous to the minute, which depends, on the one hand, on the editorial deadline and, on the other hand, on the point in time at which wastage-free printed products must be available to the shipping department. Moreover, because of increasing paper prices, the wasted paper generated when starting up a web-fed printing press must be reduced, whereby the start-up wastage should be understood as the number of printed products that are produced during start up, but that still do not meet the required quality criteria, and consequently, cannot be delivered to customers.
The decision about whether a printed product meets the quality requirements or is considered wasted paper is made taking the quality criteria of ink density, color register, and cut-off compensator into account, wherein these quality criteria must be met or complied with on all pages of the printed product.
In order to influence the ink density, color register, and cut-off compensator, a web-fed printing press comprises an ink density control, a color register adjustment, and a cut-off compensator control. The person skilled in the art who is being addressed here is familiar with these types of control devices and, as a result, they require no further explanation.
In order to print wastage-free within the shortest period of time after start-up of a web-fed printing press, the color register adjustment device, the ink density control device, and the cut-off compensator control device must be functioning within the shortest period of time using sets of parameters, whose use permits the quality criteria to be met on all pages of the printed product. Until now, there was no method known from the prior art that could guarantee this. As a result, there is a need for a method for operating a web-fed printing press, wherein printed products can be printed that meet the quality criteria of ink density, color register, and cut-off compensator within the shortest period of time while minimizing start-up wastage.
Starting herefrom, the present invention is based on the objective of creating a novel method for operating a web-fed printing press.
According to an embodiment of the invention, the following steps are executed in succession: a) a first start-up sequence is executed while using the predetermined preset parameters that are specific to the printing press and/or the print job for the color register adjustment, cut-off compensator control, and the ink density control; b) the web-fed printing press is subsequently stopped, wherein copies printed during the first start-up sequence are evaluated with respect to the color register, the cut-off compensator, and the ink density, and wherein the preset parameters for the color register adjustment and/or the cut-off compensator control and/or ink density control are adjusted as a function of this evaluation while the printing press is at a standstill; c) following this, a second start-up sequence is executed, wherein, in this connection, the preset parameters for the color register adjustment and/or the cut-off compensator control and/or the ink density control that are adjusted during the standstill are not used for printing until defined printing press speeds are reached and/or exceeded.
The inventive method provides that a first start-up sequence be executed while using the preset parameters that are specific to the printing press and/or the print job for the cut-off compensator control, the color register adjustment, and the ink density control. Subsequent to this, the web-fed printing press is stopped in order to evaluate, during the standstill, the copies printed during the first start-up sequence with respect to the ink density, color register, and cut-off compensator.
According to an embodiment of the invention, the preset parameters for the color register adjustment and/or the cut-off compensator control and/or the ink density control are adjusted during the standstill as a function of this evaluation. During a subsequent second start-up sequence, the adjusted preset parameters are used, namely as a function of reaching and/or exceeding defined printing press speeds. It is possible with the inventive method to start up a web-fed printing press within the shortest period of time while minimizing start-up wastage.
Preferred further developments of the invention are disclosed in the following description. Without being limited hereto, one exemplary embodiment of the invention is explained in greater detail on the basis of the drawing.